In general, data transmission between two circuit devices may be accomplished using connection formed by physical buses and interface ports. There are numerous common interface specifications, such as Universal Serial Bus (USB), Universal Asynchronous Receiver/Transmitter (UART), Secure Digital Input/Output (SDIO), Serial Peripheral Interface (SPI), Inter-Integrated Circuit (I2C) and so forth.
To adapt to various interface ports, it is necessary that manufacturers provide different corresponding circuit devices. For example, manufactures needs to provide circuit devices complying with USB interface ports when the USB interface is to be used; similarly, circuit devices complying with UART interface ports need be provided when the UART interface is to be used. Manufacturers are thus faced with increased manufacturing and management costs due to the demand of providing devices of having the same functions however in different versions in order to coordinate with the various interface ports.
In view of the above drawback, one of the objectives of the invention is to provide a data transmission method capable of automatic transmission interface selection and an associated circuit device, and a circuit system capable of automatic transmission interface selection.